Air humidifiers, which are used to increase the air humidity in rooms containing relatively dry air in order thus to create a room climate which is more beneficial to health, are known from the prior art. In particular, the principle of cold evaporation, in which water is stored in the container of an air humidifier and the water is brought into contact with the air by means of rotating rollers, can be used in this case. For this purpose, the room air, in turn, is drawn in from the outside and is guided with the aid of a blower via the rotating, moistened rollers, so that the air is able to absorb moisture. Devices of this type can also be used to filter particles from the air. In order to be able to reduce scaling by the water which is used, the water is cleaned, for example, in that a corresponding filter is installed in the feed line, prior to being introduced into the container or into the air humidifier. Furthermore, the water can be provided with additives which are intended to prevent bacterial contamination. Also known is the adding of fragrances in order for these to be released to the room air.